Summer annual broadleaf weed that forms light green, circular mats, up to several feet in diameter, and can spread quickly. Smooth, light green, narrow oval, or tongue-shaped leaves are displayed in whorls around the smooth stem, 3-8 leaves per node. Stems are low-growing with forked branching at nodes. Carpetweed flowers in late summer, from July to September with 2-4 tiny white flowers at the joint between leaf and stem. Spreads by seeds that germinate starting in spring and throughout the growing season. Prefers thin or sandy soils.